With the development of DNA markers (also referred to as genetic markers or gene markers), both useful and undesirable traits can be rapidly and efficiently identified when improvement in plant varieties is intended. The development of DNA markers has advanced for a wide variety of practical plants as well as for model plants such as Arabidopsis thaliana and Oryza sativa. Thus, such markers significantly contribute to improvement in plant varieties.
Plant epidemic prevention 52: 14-17, Uchida, Inoue, 1998 reports that there are at least 2 pathogenic races of powdery mildew fungi of strawberries in Japan. Also, Plant epidemic prevention 52: 14-17, Uchida, Inoue, 1998 implies that, on the basis of the results of investigation concerning sensitivity and resistance to powdery mildew fungi, powdery mildew resistance of strawberries is controlled by at least one oligogene. However, Plant epidemic prevention 52: 14-17. Uchida, Inoue, 1998 does not disclose or suggest DNA markers associated with powdery mildew resistance of strawberries.
Bulletin of the Hyogo Prefectural Technology Center for Agriculture, Forestry and Fisheries, No. 51: 7-12, Yamamoto et al., 2003 discloses that a linkage map was prepared with the use of hybrid lines of strawberry varieties “Toyonoka” and “Houkou-wase” and DNA markers detecting powdery mildew resistance were selected. Bulletin of the Hyogo Prefectural Technology Center for Agriculture, Forestry and Fisheries, No. 51: 7-12, Yamamoto et al., 2003 discloses that 29 linkage groups of “Toyonoka”-specific markers (a total of 109 markers, full-length: 1451.7 cM) and 21 linkage groups of “Houkou-wase”-specific markers (a total of 88 markers, full-length: 1205.7 cM) were obtained and that QTL analysis was conducted on the basis of the results of investigation concerning the onset of powdery mildew. According to Bulletin of the Hyogo Prefectural Technology Center for Agriculture, Forestry and Fisheries, No. 51: 7-12, Yamamoto et al., 2003, however, the LOD value attained by prospective linkage groups is about 1.22.
Summary of achievements, Miyagi Prefectural Agriculture and Horticulture Research Center, Chiba, Itabashi, 2008 discloses that resistance to strawberry powdery mildew can be attained via aggregation of a plurality of resistant genes and that linkage maps of 30 linkage groups (137 DNA markers, full length: 1,360 cM) were prepared with the use of F. virginiana (the original species) having resistance to strawberry powdery mildew-afflicted variety “Sachinoka.” According to Summary of achievements, Miyagi Prefectural Agriculture and Horticulture Research Center, Chiba, Itabashi, 2008, QTLs are designated at 3 positions as a result of the QTL analysis using the results of examination and linkage maps of strawberry powdery mildew.